A semiconductor wafer (hereinafter, workpiece) W, an example of disk-shaped workpieces includes, as shown in FIG. 7 in an enlarged scale, sloped edges Ea, Eb each formed by chamfering the outer peripheral edge of the front surface and the rear surface, and such edges Ea, Eb are polished by an outer periphery polishing apparatus. Patent Literature (PTL) 1 discloses the outer periphery polishing apparatus for polishing such edges.
As shown in FIG. 7 and FIG. 8 schematically illustrating the case of polishing the edge Eb on the rear surface side, the outer periphery polishing apparatus includes a polishing member 100 formed by attaching a polishing pad 102 onto an arcuate pad attaching surface 101a of a pad holder 101. An arcuate working surface 103 formed of the polishing pad 102 is tilted to be parallel to the edge Eb and brought into surface-to-surface contact with the edge Eb, and the workpiece W is made to rotate about a vertical axial line while maintaining the surface-to-surface contact, to thereby polish the edge Eb with the working surface 103. At this moment the polishing member 100 is made to slowly reciprocate by a non-illustrated reciprocation mechanism along a straight line (reciprocation line L) parallel to the edge Eb, so that the entirety of the working surface 103 is utilized for polishing the edge Eb.
The outer periphery polishing apparatus is configured to polish the edge Eb of the workpiece W maintaining the arcuate working surface 103 of the polishing member 100 in surface-to-surface contact with the edge Eb as mentioned above, and hence provides excellent polishing efficiency. However, a tilt angle α of the working surface 103 and the reciprocation line L with respect to a horizontal plane S is fixed to a predetermined angle, and therefore only such workpieces having a bevel angle θ (angle between edge and front surface or rear surface of the workpiece) equal to the tilt angle α can be polished, which is an aspect to be improved. The bevel angle of the edge is not the same but varies in each of the workpieces, and therefore there has been a demand for a mechanism to adjust the tilt angle α of the working surface 103 and the reciprocation line L to the bevel angle of the workpiece, so as to polish the workpieces having different bevel angles.
On the other hand, PTL 2 and PTL 3 disclose a polishing apparatus configured to relatively tilt the polishing element with respect to the workpiece, so as to polish the entirety of the edge by adjusting the contact angle of the polishing element with respect to the workpiece.
However, the cited polishing apparatus is configured to polish the edge while gradually changing the contact angle of the polishing element with respect to the workpiece, and therefore the configuration and working are fundamentally different from those of the outer periphery polishing apparatus according to PTL 1. Accordingly, the technique according to PTL 2 and PTL 3 is unable to be applied as it is to the outer periphery polishing apparatus.